جستجوی مقالات مرتبط با کلیدواژه « لیپولیز » در نشریات گروه « پزشکی »

Fat reduction adversely affects different properties of cheese. Transglutaminase treatment of low-fat milk incorporated with whey proteins makes it possible to develop a low-fat white-brined cheese with rheological properties similar to the full-fat counterpart. The objective of this study was to monitor the changes in proteolysis and lipolysis indices of transglutaminase–treated low-fat white-brined cheese during ripening. A control full-fat (3% fat), a control low-fat (1% fat) and an enzyme-treated low-fat (1% fat, 0.9 U transglutaminase/g protein, 5% whey protein isolate/L milk) white-brined cheese were produced and their physicochemical properties, proteolysis and lipolysis indices, FFA profile and organoleptic attributes were studied after 3, 20, 40 and 60 days. The proteolysis and lipolysis indices of all samples showed an increasing trend during ripening (p<0.05). The development of proteolysis and lipolysis in white-brined cheese with reduced fat content was noticeably slower than its full-fat counterpart (p<0.05). Transglutaminase treatment of low-fat milk incorporated with whey proteins retarded the syneresis of resultant cheese and hereby promoted its extent of proteolysis and lipolysis (p<0.05). The decreasing rate of short-chain free fatty acids production was more pronounced than that of medium- and long-chain free fatty acids, due possibly to their contribution to production of flavor compounds. Flavor of enzyme-treated low-fat cheese was considerably improved during ripening (p<0.05) but was less appreciated by consumers than that of control full-fat sample (p<0.05). Transglutaminase treatment of low-fat milk incorporated with whey proteins results in a low-fat white-brined cheese with accelerated proteolysis and lipolysis and thus, more desirable organoleptic properties.

Lipolysis during cheese ripening is one of the main biochemical reactions. In pasteurization natural lipase present in milk becomes inactive. Therefore lipolysis occurs in Iranian cheeses at low level. The aim of this study is to accelerate the ripening of traditional and ultra-filtered Feta cheeses by lipolysis and evaluate the effect on the microbiological characteristics of the cheeses. Aspergillus niger encapsulated lipase was prepared according to Sol-Gel method. For producing cheeses after milk fat standardization where the pasteurization was carried out at 75 °C for 15 s, the milk was cooled and the starter, rennet and lipase were added in three forms of encapsulated, encapsulated with arabic gum and non- encapsulated to the traditional and UF-Feta cheeses. The amount of added lipase to curd or retentate was 4 g/100kg. The lipolysis development and evaluations of chemical, microbial and sensory characteristics were performed during the 60 days of ripening. On the 15th day of ripening period the lipolysis development and chemical compounds observed had significant differences at the P< 0.05 between the traditional and UF- Feta cheeses. The microbial counts were negative after 15 th day.Encapsulated lipase treatment of UF-Feta cheeses had the highest sensory score. Accelerated lipolysis in cheese might be regarded as a ripening indicator. Production of free fatty acid and hygroscopic additive like arabic gum had prevention effect on microbial counts in the final product and improved the sensory properties.

The purpose of the present study was to investigate the combined effects of endurance training and fasting during Ramadan on fat and carbohydrate metabolism. Twenty four healthy men (age، 25. 4±2. 3 years) were randomly allocated to two groups of fasting (F، n=12) and fasting + endurance training (F+ET، n=12). The study protocol for the F group included 10 and the F+ET group had 12 subjects. The fasting group only fasted during Ramadan، whereas the F+ET group، in addition to fasting، performed three sessions of endurance training on the treadmill after Iftar. Antropometric indices، blood samples and dietary intakes were documented the beginning of Ramadan and after the first week and at the end of Ramadan. Weight and body mass index did not change significantly during Ramadan in either group (P>0. 05)، but the body fat percentage reduced significantly (P<0. 05) during Ramadan in both groups. Fat oxidation، carbohydrate oxidation، insulin، glucose، glycerol، and non-esterified free fatty acid changed in the first week of Ramadan، more pronouncedly in F+ET group، whereas in the F group these changes occurred more during the second half of the Ramadan، though the changes did not differ significantly between the two groups. Combining Ramadan fasting and exercise training affects the trend of changes in fat and carbohydrate oxidation during Ramadan. Generally however the effects of two protocols were similar and adding the endurance training to fasting did not induce more changes than fasting perse.

This study examined the effects of circuit resistance exercise on fat and carbohydrate metabolism during endurance exercise in overweight men.

Ten overweight men (mean±SD: age, 28.8±4.8 yr; BMI, 28.2±1.4 kg/m2; vo2max, 23.3±3.7 ml/kg/min) performed two types of exercise regimens: 1) Endurance exercise (E), and 2) Circuit resistance exercise, followed by endurance exercise (RE). Circuit resistance exercise consisted of six stations, each with three circuits at 50% of 1-RM (one repetition maximum), and a total exercise time of 21 min. Endurance exercise consisted cycle ergometer exercise at 60% of the maximal oxygen uptake for 30 min. Expired gases at rest, before and during endurance exercise were measured for calculating fat and carbohydrate oxidation. Venous blood samples were taken at rest, before and immediately after endurance exercise. Blood samples were analyzed for glucose, nonestrified fatty acids (NEFA), malonyl COA (MCOA), glycerol and insulin.

Plasma glycerol concentrations during endurance exercise increased 53% in RE vs. 46% in the E group (P<0.001). Concentration of plasma glucose before endurance exercise was higher in RE than in the E group (P<0.001). In RE exercise, although fat oxidation through the 30-min endurance exercise (mean value) was greater than in the E regimen, there was no significant difference between the two groups (P>0.05). Also, no significant difference was observed in the NEFA, MCOA, insulin, carbohydrate oxidation responses (P>0.05).

Lipolysis during the submaximal exercise is enhanced by prior circuit resistance exercise in overweight men.

Iranian white cheese is a type of cheese ripened in brine with high concentrations of Sodium Chloride (NaCl). The brine influences curd development in the process of making cheese and its shelf-life. However, considering that NaCl increases the risk of cardiovascular and renal diseases, cheese producers try to replace it with substitutes, such as potassium chloride. Iranian white cheese samples prepared using pasteurized cow’s milk were ripened in different brines containing either 10% NaCl (control) or a mixture of NaCl/KCl with ratios of 1:1 and 3:1 (case). The effect of partial substitution of NaCl by KCl was investigated on the chemical composition, proteolysis, and lipolysis, as well as on the physical properties (textural hardness) of the cheese samples during ripening for up to 56 days. Lipolysis was assessed by measuring acid degree value (ADV). The physical and chemical properties (dry solids, salt, pH, and acidity) of the experimental and control cheese samples were not significantly different. Neither were there any significant differences with regard to proteolysis (measured by Kjeldhal method and electrophoresis). Finally, substituting NaCl with KCl had no effect on ADV or textural hardness of the experimental samples either. It can be concluded that a reduction of NaCl up to 50% in brine has no effect on the quality of the cheese produced. Furthermore, substituting NaCl with KCl will not cause noticeable changes in ADV and textural properties of the cheese.